1. Field of the Invention
The present invention generally relates to liquid-crystal display devices and methods of fabricating the same, and more particularly to a Thin Film Transistor (TFT) liquid-crystal display device and a method of fabricating the same.
2. Description of the Related Art
Recently, liquid-crystal display devices for use with information processors such as computers are widely used because of their portable size and low power consumption.
Especially to realize high quality color display, an active matrix method that controls each pixel electrode is widely applied to liquid-crystal display devices.
FIG. 1 shows a diagram of a conventional active-matrix-type liquid-crystal display device. Referring to FIG. 1, a liquid-crystal display device 10 includes a first TFT glass base 11 having a plurality of TFTs and transparent pixel electrodes cooperating therewith and a second glass base 12. A liquid-crystal layer 1 between the first TFT glass base 11 and the second glass base 12 is sealed by sealing members. In the liquid-crystal display device 10, the transparent pixel electrode may be selected turned ON through the TFT so that a orienting direction of liquid-crystal molecules is altered by the selected transparent pixel electrode. A polarization plate (not shown) is arranged in a cross Nicol state. Moreover, molecule orientation films are provided inside of the TFT glass base 11 and the glass base 12 to suppress orienting directions of liquid-crystal molecules.
FIG. 2 shows a part of the TFT glass base 11 under magnification.
Referring to FIG. 2, on the TFT glass base 11, a plurality of pad electrodes 11A supply scan signals and a plurality of scan electrodes 11a are extend therefrom. Also, a plurality of pad electrodes 11B supply image signals and a plurality of signal electrodes 11b are extended therefrom. The extending direction of the scan electrodes 11a and that of signal electrodes 11b cross each other. TFTs 11C are provided at every point of intersection of the scan electrodes 11a and signal electrodes 11b. Furthermore, a transparent pixel electrode 11D is provided to each TFT 11C. A row of TFTs 11C is selected by a scan signal from a corresponding scan electrode 11a and then a particular transparent pixel electrode 11D is operated by an image signal from a corresponding signal electrode 11b. 
FIGS. 3A, 3B, 3C and 3D show sectional views illustrating production steps of a conventional liquid-crystal display device. In these figures, every left side shows a display area including a TFT 11C and every right side shows a terminal area including pad electrodes 11A and 11B.
Referring to FIG. 3A, in the display area, an Alxe2x80x94Nd or Alxe2x80x94Sc alloy pattern 22A that is connected to the scan electrode 11a is formed as a gate electrode 22A on a glass base 21 corresponding to the first TFT glass base 11 in FIG. 1. Simultaneously, in the terminal area on the glass base 21, terminal electrodes 22B, which are made up of an Alxe2x80x94Nd or Alxe2x80x94Sc alloy pattern, corresponding to the pad electrode 11A or 11B are formed.
Subsequently, in the display area in FIG. 3B, a gate insulation film 23A that is made up of SiN is layered over the gate electrode 22A. Moreover, an nxe2x88x92type impurity doped amorphous silicon layer 24A is layered over the gate insulation film 23A. Furthermore, a channel mask film 25A, which is made up of SiN, is formed on an area corresponding to a channel region right above the gate electrode 22A and is etched.
In the terminal area in FIG. 3B, an insulation film 23B, which is made up of the same composition (SiN) and thickness as the insulation film 23A, is layered over the terminal electrodes 22B and then an amorphous silicon layer 24B, having the same thickness as the amorphous silicon layer 24A, is layered over the insulation film 23B.
In addition, in the display area in FIG. 3C, an n+type impurity doped amorphous silicon pattern 26A is formed on the amorphous silicon layer 24A and is adjoined with sides of the channel mask film 25A. Moreover, a metal is layered on the n+type impurity doped amorphous silicon pattern 26A so that a source-drain of the TFT 11C is constituted. For example, the above metal can be constructed by Ti, Al and Ti layers.
Subsequently, in the display area in FIG. 3D, a mask film 27A, which is made up of SiN, is layered so as to cover over the n+type impurity doped amorphous silicon and metal pattern 26A and the channel mask film 25A on the gate insulation film 23A. In addition, a contact hole 28A is provided in the mask film 27A at one side of the amorphous silicon pattern 26A. Furthermore, a transparent pixel electrode 29 is provided at the contact hole 28A and contacts the amorphous silicon pattern 26A. The transparent pixel electrode 29 corresponds to the transparent pixel electrode 11D in FIG. 2.
Simultaneously with steps in the display area in FIG. 3D, in the terminal area in FIG. 3D, a mask film 27B corresponding to the mask film 27A is layered on the insulation film 23B. Then contact holes 28B are formed to expose the terminal electrodes 22B. As shown in FIG. 4, in a liquid-crystal display device 52, IC devices 56 are connected to the terminal electrodes 22B via the contact holes 28B in the terminal area on a display panel 54 by tape automated bonding (TAB) leads (not shown).
The second glass base covers and seals the display area on the TFT glass base 21.
Generally, to cut production cost, after a plurality of liquid-crystal displays are produced on a surface of a large glass base, the large glass base is cut into each liquid-crystal display so that a plurality of liquid-crystal display devices are completed.
FIG. 5 is a sectional view illustrating the conventional liquid-crystal display device after a cutting step. Referring to FIG. 5, a first glass base 40, corresponding to the first TFT glass base 11 in FIG. 1, has a terminal area 47 including terminal electrodes 22B and a display area 48 surrounded by the terminal area 47. The first glass base 40 is sealed with a second glass base 49, sealing members 42 and spacers (not shown) such that the first glass base 40 and the second glass base 49 face each other. The terminal area 47 is not covered with the second glass base 49. Thus, the terminal area 47 is vulnerable to particles especially during the cutting step. In particular, when terminal electrodes 22B in the terminal area 47 are damaged mechanically by the particles, the damage makes it impossible to connect the liquid-crystal display to external circuits so that functions as a liquid-crystal display are lost.
It is a general object of the present invention to provide a Thin Film Transistor (TFT) liquid-crystal display device and method of the same in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a Thin Film Transistor (TFT) liquid-crystal display device and a method of fabricating the same that prevent particles from causing mechanical damages and improve yield of production of the same.
The above objects of the present invention are achieved by a liquid-crystal display device including: a first glass base; a second glass base facing the first glass base in a condition in which a space is defined between the first glass base and the second glass base; a liquid-crystal layer filling the space between the first glass base and the second glass base, and being sealed inside the first glass base, the second glass base and supporting members; a display area that is a surface area of the first glass base and faces the second glass base, and that includes thin-film transistors; a terminal area having terminal electrodes that connect electrically to corresponding thin-film transistors respectively; and projections provided on the terminal area such that heights of the projections are equal to or more than those of the thin-film transistors.
According to the present invention, the projections are provided in the terminal area so as to prevent terminal electrodes from damages caused by particles.
The objects of the present invention are also achieved by a method for producing a liquid-crystal display including the steps of: (a) forming a display area having thin-film transistors on a first glass base which surface faces a second glass base; and (b) forming a terminal area having terminal electrodes that connect electrically to the thin-film transistors respectively in a condition in which projections are provided in the terminal area and heights of the projections are substantially equal to or more than those of the thin film transistors.
According to the present invention, the projections are provided during the steps for producing the display area and the terminal area. In addition, the projections are made up of the same components as the thin-film transistors. Therefore, the projections can be provided without requiring any extra steps or any extra components.